A prior art notching machine of the kind as herein referred is described in U.S. Pat. No. 4,483,227. In this known notching machine a blade assembly is being used that comprises an upper knife and a lower knife that are respectively mounted on a projecting head serving as a tool holder of a vertically moving ram and on the machine table. The upper and the lower knives are each composed of two individual blades which with their cutting edges confine a vertex angle on a nose portion of each knife to thusly allow a notching of workpieces with a notching angle that corresponds to this vertex angle. For now providing notchings in workpieces of any desired size of angle this known notching machine is further provided with means that allow to change the vertex angle by turning the two blades of each knife relative to each other around a vertical axis of rotation that extends in parallel with the ram near the noses of the upper and lower knives. With this possibility a notching machine is being presented which allows a variable notching of workpieces over a consumer-oriented working range between for example an angle of 30.degree. and an angle up to 120.degree. or more whereby each notching with any desired angle within this particular range of adjustment for the two blades of each upper and lower knife is being effected by a single working stroke of the ram. Under consideration thereof that the cutting capacity of such notching machines is usually rated by a reference to the blade life and in particular to that of a upper knife at its most critical nose portion this prior notching machine, however, presents the disadvantage that each of the two blades of the upper knife as well as of those of the lower knife of the blade assembly must be provided with a vertex angle of 15.degree. for allowing a notching of workpieces with a minimum notching angle of 30.degree.. Since such a corresponding minimum vertex angle of 15.degree. provides a much shorter blade life than for example a vertex angle of 30.degree. these known notching machines are usually equipped with at least two sets of blades for the upper knife of the blade assembly whereby the two blades of the one set are each provided with a vertex angle of 15.degree. whereas the two blades of the second set are each provided with a vertex angle of 30.degree.. The blades with the smaller vertex angle are then usable for notching angles from 30.degree. to 60.degree. whereas the blades with the larger vertex angle cover the remaining range of variable notching angles from 60.degree. to 120.degree. or 135.degree. so that with the use of such a second set of blades at least for the upper knife of the blade assembly an overall cutting capacity will be obtained that can be considered as superior in comparison with a notching machine which is only equipped with the one set of blades for covering the entire range of notching angles.
This invention deals with the object of providing a notching machine allowing the notching of workpieces with any desired notching angle by using a blade assembly of which the nose portion at least of the upper knife underlies a less critical load condition to thereby obtain an overall blade life which when high-lighted on certain preferred notching angles of the variably adjustable range will more or less correspond with the blade life of a corresponding number of upper knives each having a fixed vertex angle of the corresponding different sizes. According to a further object of the invention there shall also be provided a notching machine having a blade assembly of which at least the upper knife when set up at its nose portion to any particular consumer-oriented vertex angle then of course along a correspondingly adjusted vertex angle of the lower knife provides a cutting capacity or blade life which for such a particular vertex angle corresponds to the one of an upper knife having the corresponding fixed vertex angle as confined by two cutting edges.
According to the present invention there is provided a notching machine having a blade assembly of which at least the upper knife comprises a third blade component for forming its nose portion and having a unitary cutting edge that complements the cutting edges of the two other blades of the upper knife for confining its vertex angle whereby this third blade component is being mounted interchangeably on the tool holder at the projecting head of the machine's vertically moving ram and is being made available with differently sized vertex angles and/or with different contours of the cutting edge.
The notching machine of the present invention accordingly allows the notching of workpieces with any desired notching angle each with a single working stroke of the machine's vertically moving ram and each with the use of an upper knife of the blade assembly the two primary blades of which then have before been adjusted along a corresponding adjustment of the two blades of the lower knife to the corresponding vertex angle which at least for this upper knife then also has been before provided by mounting the particular third blade component on the tool holder of the ram's projecting head. Under consideration thereof that for a variable range of notching angles between 30.degree. and 135.degree. the common consumer-oriented use mostly calls for the availability of eight differently sized vertex angles differing from each other in an ascending sequence by an angle of 15.degree. it then should be realized that the notching machine of this invention must only be equipped with eight of such third blade components having the differently sized vertex angles each at a unitary cutting edge that complements the cutting edges of the two other blades of the upper knife. When using such third components as the nose portion at least of the upper knife this of course substantially reduces the overall costs of the blade assembly besides of guaranteeing an encouraging overall blade life.